We removed SVN for the windows installer since the verison 1.0.10-4. If you want to use Trac & SVN in Windows, we can provide you an older installer.
Also, we are still shipping SVN in the Linux and OSX installers, so you can use the latest version in those platforms.
You can also use one the Bitnami Trac VMs and use Trac with VMWare or VBox on a Windows system. Those VMs include a Debian distribution and ship SVN. You can download them from this link.